Marshall PT current ratings

[Roffe]

A separate heater transformer may induce hum. It should be mounted at the outside/on top of a steel chassis and preferably have endbells and/or a copper flux band. Also its orientation may matter.

Thanks, that’s good to know. The top of the amp is steel so I’m good there. Can I add a flux band by wrapping a turn of copper foil around the core in the winding direction?

[Helmholtz]

Can I add a flux band by wrapping a turn of copper foil around the core in the winding direction?

I would think so. Just make sure that the foil is not too thin and is well soldered across its width to provide a perfect shorted "turn".

[Roffe]

Just a little update: I tested the heaters with all tubes inserted and no load on the HT, I’m getting 6.5V so I think I’m good voltage-wise. A little high since I have 230V on the 220V primary, but it will probably drop a bit when I connect the rest of the circuit. I’ll just keep an eye on the temperature, but I think this will work out.

[Chuck H]

So if you were on a 220V outlet that would be about 6.22V. This stuff is rarely exact but if we take the numbers at face value that's a drop of only .08V. So yeah, I'd say you're probably good to go.

[wamisur]

just power it up with the Marshall PT and see what you have for filament voltage

[wamisur]

just power it up with the Marshall PT and see what you have for filament voltage

If the filament winding drops way below 6.3V, you'll know it's being stressed too much.

[shukam56m]

I think you can use your PT provided it runs cooler than in the original Marshall amp.

[shukam56m]

This stuff is rarely exact but if we take the numbers at face value that's a drop of only .08V. So yeah, I'd say you're probably good to go. i

[Helmholtz]

This thread is from 2020.

[g1]

This thread is from 2020.

They are posting very credible messages with invisible spam links. They probably come back later and make them visible.

[Chuck H]

They are posting very credible messages with invisible spam links. They probably come back later and make them visible.

And I'm watching for that. I did look up IP locations already and there's nothing obviously spammy about them, yet.